1. Field of the Invention
The invention relates to a process for the preparation of organosilanes in an efficient manner, such that the yield of a preferred product is increased. With more particularity, the invention relates to a process for the preparation of organosilanes in an efficient manner by reacting a molar excess of an alkene halide with a hydrogen silane.
2. Description of the Related Art
Organosilanes may be produced by the reaction of an alkene halide with a hydrogen silane and can be represented by the following equation:
RbXaSiH4xe2x88x92axe2x88x92b+Rcxe2x80x2Yxe2x86x92RbH3xe2x88x92axe2x88x92bXaSiRxe2x80x2Yxe2x80x83xe2x80x83Reaction 1
Where R is selected from the group consisting of alkyls having one to about 20 carbons, cycloalkyls having from 4 to 12 carbons and aryls; X is a halogen; Rxe2x80x2 is an alkyl having from one to twenty carbons and Y is a halogen; a=0 to 3, b=0 to 3; and a+b=1 to 3.
Particularly useful organosilanes include halopropylorganosilanes that are common intermediate materials in organosilane chemistry.
Halopropylorganosilanes are generally prepared by a catalyzed reaction of an allyl halide with a hydrogen silane in a hydrosilation or hydrosilyation process and can be described by the following general reaction equation:
RbXaSiH4xe2x88x92axe2x88x92b+CH2CHCH2Yxe2x86x92RbH3xe2x88x92axe2x88x92bXaSiCH2CH2CH2Yxe2x80x83xe2x80x83Reaction 2
Where R is selected from the group consisting of alkyls having one to about 20 carbons, cycloalkyls having from 4 to 12 carbons and aryls; X is a halogen; and Y is a halogen; a=0 to 3, b=0 to 3; and a+b=1 to 3.
The hydrosilation reaction is accompanied by an undesired side reaction to produce a by product propylorganosilane and can be described by the following general reaction equation:
RbXaSiH4xe2x88x92axe2x88x92b+CH2CHCH2Yxe2x86x92RbXaH3xe2x88x92axe2x88x92bSiCH2CH2CH3+RbXaSiH3xe2x88x92axe2x88x92bYxe2x80x83xe2x80x83Reaction 3
Where R is selected from the group consisting of alkyls having one to about 20 carbons, cycloalkyls having from 4 to 12 carbons and aryls; X is a halogen; and Y is a halogen; a=0 to 3, b=0 to 3; and a+b=1 to 3.
A common halopropylorganosilane utilized in the chemical industry is chloropropyltrichlorosilane which is produced from the reaction of trichlorosilane and allyl chloride according to the following reaction equation:
Cl3SiH+CH2CHCH2Clxe2x86x92Cl3SiCH2CH2CH2Clxe2x80x83xe2x80x83Reaction 4
The by product, propyltrichlorosilane is produced from a secondary reaction and can be represented by the following reaction equation:
2Cl3SiHxe2x86x92CH2CHCH2Clxe2x86x92Cl3SiCH2CH2CH3+SiCl4xe2x80x83xe2x80x83Reaction 5
It is known in the art that the efficiency of a process for producing halopropylorganosilanes can be improved if the amount of the undesirable by product can be reduced. For example, U.S. Pat. No. 6,242,630 discloses a process for the continuous preparation of halopropylorganosilanes wherein the reaction carried out is a partial reaction of from 10% to 80% on a molar basis of the starting materials. This process requires complex control and monitoring to maintain the process conditions; thereby increasing the costs of the process.
U.S. Pat. No. 5,177,236 discloses a process for the preparation of chloropropyltrichlorosilane from a hydrogen silane and allyl chloride wherein the reaction temperature is maintained at the boiling point of the higher boiling point reactant. The reaction takes place in the presence of a platinum containing carrier material which is located above the reactant mixture. The vapors of the reactant mixture are conducted through a condenser which bypasses the carrier material. The condensate is then passed through the carrier material into the boiling reactant mixture. The condensate formed in the condenser contains a stoichiometric excess of allyl chloride based on the hydrogen silane reaction compound. This process is again complex, and requires a high energy load to vaporize the reactants. The vaporization of the reactants also limits the excess amount of allyl chloride possible for reaction, as an equilibrium will be maintained between the vapor and boiling liquid of allyl chloride. The vaporization of the reactants also limits the amount of excess allyl chloride in that the rate of vaporization of the reactants will limit the amount of allyl chloride in the condensate.
There is, therefore, a need in the art to provide a cost and energy efficient process for the production of a halopropylorganosilane that minimizes the production of an undesired by product.
The present invention is a process for producing organosilanes including reacting an alkene halide with a hydrogen silane in the presence of a hydrosilating catalyst. The alkene halide and hydrogen silane are maintained in a liquid phase. The alkene halide is present in an amount such that a molar excess of at least 1.1 moles of alkene halide per mole of hydrogen silane is maintained.
The process of the present invention has the advantage of providing a process that does not require complex control or monitoring or require a high energy load to produce the desired product.
The process of the present invention also provides the advantage of increasing the yield of a desired product in relation to the undesired product that results in a higher silicon efficiency and lower process waste.
The process of the present invention has the further advantage of providing a process that has a reaction in a liquid phase utilizing liquid reactants that do not require the use of a high energy load, and are easy to process.